Lichen

:For other things named "lichen", see: Lichen (disambiguation).

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Lichens are symbiotic organisms made up by the association of microscopic green algae or cyanobacteria and filamentous fungi. Lichens take the external shape of the fungal partner and hence are named based on the fungus. The fungus most commonly forms the majority of the lichen's bulk, though in filamentous and gelatinous lichens this may not always be the case. The lichen fungus is typically a member of the Ascomycota—rarely a member of the Basidiomycota. Some lichen taxonomists place lichens in their own division, the Mycophycophyta, but this practice ignores the fact that the components belong to separate lineages.

Related Topics:
Symbiotic - Green alga - Cyanobacteria - Fungi - Ascomycota - Basidiomycota - Lineages

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The algal cells contain chlorophyll, permitting them to live in a purely mineral environment by producing their own organic compounds (see photosynthesis). The fungus protects the alga against drying out and, in some cases, provides it with minerals obtained from the substratum. If a cyanobacterium, such as in Terricolous Lichens, is present this can fix atmospheric nitrogen, complementing the activities of the green alga.

Related Topics:
Chlorophyll - Photosynthesis - Substratum - Cyanobacterium - Terricolous Lichens - Fix atmospheric nitrogen

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